August 20, 1896] 



NATURE 



379 



• ON PERIODICITY OF GOOD AND BAD 



SEASONS.^ 

 T FEEL some reluctance in coming forwaril tonight, with the 

 result of my investigations into the peiioclicity of good and 

 bad seasons— floods and droughts if you will— because they must 

 come to you as a surprise, and they will make a claim on your 

 confidence which at first sight you will probably not be disposed 

 to grant. I-'or myself I know that some years ago, if any one 

 had come to me stating thit it was possible to forecast the 

 seasons many years in advance, I should have received the state- 

 ment with incredulity. The difficulty in getting the facts to- 

 gether is very great. I have had to ask from history records of 

 passing phenomena which it has been the habit of the historian 

 to neglect ; however, there will be before you a mass of evidence 

 in support of my proposition, //lat tlio;- is a periodicily in 

 ■weather. The weak point in the evidence is that history has 

 not kept a regular and continuous account of droughts, but only 

 recorded them when they became very prominent. The strong 

 point is that all the data that history does give us is in favour of 

 the nineteen years' cycle. 



And it may be e.\plained that the word drought is not used 

 here in the sense in which it is often used in England and else- 

 where, that is, to signify a period of a few days or weeks in 

 which not a drop of rain falls ; but it is used to signify a period 

 of months or years during which little rain falls, and the country 

 gets burnt up, grass and water disappear, crops become worth- 

 less, and sheep and cattle die. 



Drought is, however, not wholly made by a deficiency of 

 r.ainfall. Its most important factors are great heat and drying 

 winds. As an illustration we may look to the year 1895 > '" ^^ 

 latter part of winter and in spring there were many falls of rain, 

 which would have made grass in ordinary seasons, although there 

 was not as much as usual, but it had no sooner fallen than a dry 

 north-west w ind and burning sun dried it all up. This great 

 and burning heat was a well-known feature in historical 

 droughts, and some authorities say that the fable of I'haeton 

 driving the chariot of the Sun so close to the earth that he set 

 it on fire, is a poetical setting of an actual experience in Greece 

 when the sun became so powerful that the heat was almost 

 beyond endurance. 



Before 1895 ^" 'he diagrams I used had been made to show 

 quantities of the various elements, and their relation in time, with 

 a view to seeing if there was any periodicily. Recently it occurred 

 to me that it would be useful to have a diagram in which all the 

 droughts, without regard to their intensity, should be placed in 

 their order of time ; not only was this desirable for seeing what 

 the relation in time was, but it had become evident that it would 

 be impossible to see the relation between our droughts and those 

 in other countries, unless some such pictorial arrangement was 

 made. 



As a preliminary to making the diagram, the particulars of the 

 weather in this colony from all sources, for every year of our 

 history, were carefully examined, and the years simply classed 

 as good or bad ; that is, having sufficient or insufficient rainfall. 

 A form was then prepared with a vertical space for each year, 

 and across these a zero line was drawn to divide the good from 

 the bad ; and, beginning with 1895, I filled in for that year, and 

 below the line, a convenient length of the column in red ink ; the 

 length was simply to catch the eye. Then for 1894, a good 

 year, I filled in with black ink, above the line, a sp.ice equal to 

 the red in the vertical space for 1894. The two years were thus 

 contrasted simply as good and bad ; the question of how good, 

 or how bad, was pur]50Sely left out. The diagram was then 

 completed, each year being treated in the same way back to 

 1788. It was at once apparent that a drought lasting from three 

 to seven years was most regular in its occurrence, h. vertical 

 red line .was then drawn between the first and second years 

 of each of these dry periods, and it was found that the interval 

 between two successive lines was regular and exactly nineteen 

 years. The centres of another set of dry periods, more intense 

 and relatively shorter than the first series, were found also to 

 recur at intervals of nineteen years. One of these droughts 

 falls regularly between a pair of the more extensive droughts 

 previously referred to. 



In the whole period, from the foundation of the colony of 

 New South Wales to the present year, i.e. 108 years, it is 

 certainly very noteworthy that the most jjronounced droughts 



' Abridged from a paper read before the Roy.il Society of New South 

 Wales, June 3, by H. C. Russell, C M.G., F.R.S. 



NO. 1399, VOL. 54] 



recur with great regularity — that is, at every nineteen years 

 throughout the 108 years. Indian droughts seem to have 

 coincided with Australian ones in many instances. 



The investigation had become interesting, and seemed to 

 promise to show the exact year of the great drought in this country, 

 of which there was abundant evidence when the colonists 

 landed here, both in the fact that to the south of Sydney all the 

 very large trees were dead, and between thein were growing 

 young trees ; and the story of the blacks, who said that the river 

 Hunter dried up ; that all the great trees died, and most of the 

 blacks ; that those who survived had obtained drinking-water 

 from the mountain springs. I had long wanted to find out 

 when this terrible drought in this colony took place, and the 

 Indian record showed that the extensive drought had been 

 repeated in 1769-70, which probably fi.xes the date; for the 

 middle of the eighteenth century was very dry, generally, all over 

 the world. 



But, if we can carry the nineteen years' period in this way back 

 beyond our history, the idea immediately presents itself, where 

 are you going . to draw the limit, is there any limit ? It was 

 evidently not a question for argument, but for proof or disproof 

 by figures. Tables were prepared showing every date on which 

 droughts of the first class recurred back to A. D. I, and the same 

 for droughts of the second class. I am not going to weary you 

 by going through the list, but will give you the result. History 

 says very little about droughts prior to A.n. 900. Between that 

 date and this, a drought has, on the assumption, occurred at 

 every nineteen years. In this interval of nine hundred and ninety- 

 six years there have been fifty-two repetitions of drought, and 

 the question is what has history to say about its droughts. Well, 

 it shows that these droughts have been repeated at various places 

 on the earth on forty-four of the fifty-two dates ; of these eight 

 missing droughts, no less than six of them occurred between 1000 

 and 900 A. I)., an interval when history was less complete on these 

 matters. So far as I have gone, history furnishes us with seventy- 

 eight droughts in different countries, all of which fit into the 

 first series. During the same period, droughts of the second 

 series recurred fifly-one times, and history records droughts, 

 numbering eighty-nine, on thirty-six of these periods. Taking 

 then the droughts history has recorded between a.d. 900 and 

 1896, we have seventy-eight of the first series and eighty-nine of 

 the second, a total of one hundred and sixty-seven, out of two 

 hundred and eight on record ; but this is not all, for another 

 class of drought, which is irregular in Australia, seems to be more 

 definite and important in the northern hemisphere, and twenty- 

 six more out of the two hundred and eight belong to this series, 

 making up the number to one hundred and ninety-three out of 

 the total of two hundred and eight. 



In estimating the importance of these figures, it must be re- 

 membered that, before 1788, North and South America, Russia, 

 China, Per.sia, Turkey, Austria and Australia, all subject to fre- 

 quent drought, yet did not, however, furnish to the numbers 

 quoted more than you could count on your fingers ; and it may be 

 fairly assumed that if we had these records, and especially if 

 history had made a |3oint of recording droughts, we should have 

 had drought recorded on every recurrence of the nineteen years' 

 cycle, of the two chief series ; but I think the evidence that his- 

 tory furnishes one hundred and ninety-three recorded droughts, 

 ever)' one of which fits into the cycle, justifies us in assuming 

 that the nineteen years' cycle has been running for at least one 

 thousand years, and may be trusted to continue and justify fore- 

 casts based upon it for some time to come. 



Having got so much from the study of droughts in the Chris- 

 tian era, it seemed desirable to see if there were any recorded in 

 B.C. times. Records of twenty B.C. droughts were found, all of 

 which, with one exception, fit into our nineteen years' cycle. 

 If these dates are examined apart from their connection with 

 Australian droughts, we find that the intervals between them 

 are multiples of nineteen years, which shows that droughts then, 

 as now, occurred in cycles of nineteen years, which is very 

 strong evidence in favour of our theory, the more so when it is 

 remembered that all the B.C. droughts I have been able to col- 

 lect, except one, do fit in : they do not form a series of droughts 

 selected for the purpose of supporting it ; again, taking the 

 dates given in the various works, the intervals between all these 

 B.C. droughts and those in Australia are multiples of nineteen 

 years. 



If it be objected that chronologists have grave doubts about 

 the accuracy of b.C. dates, I reply, that it is quite certain that 

 chronologists did not arrange the dates to make them fit into an 



